Biological invasions have been identified as the fifth cause of biodiversity loss, and their subsequent dispersal represents a major ecological challenge. The aquatic invasive species Ludwigia grandiflora subsp. hexapetala ( Lgh ) and Ludwigia peploides subsp. montevidensis ( Lpm ) are largely distributed in aquatic environments in North America and in Europe. However, they also present worrying terrestrial forms that are able to colonize wet meadows. To comprehend the mechanisms of the terrestrial adaptation of Lgh and Lpm , it is necessary to develop their genomic resources, which are currently poorly documented. We performed de novo assembly of the mitogenomes of Lgh and Lpm through hybrid assemblies, combining short reads (SR) and/or long reads (LR) before annotating both mitogenomes. We successfully assembled the mitogenomes of Lgh and Lpm into two circular molecules each, resulting in a combined total length of 711,578 bp and 722,518 bp, respectively. Notably, both the Lgh and Lpm molecules contained plastome-origin sequences, comprising 7.8% of the mitochondrial genome length. Additionally, we identified recombinations that were mediated by large repeats, suggesting the presence of multiple alternative conformations. In conclusion, our study presents the first high-quality mitogenomes of Lpm and Lgh , which are the only ones in the Myrtales order found as two circular molecules.

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Epipogium roseum , commonly known as one of the ghost orchids due to its rarity and almost transparent color, is a non-photosynthetic and fully mycoheterotrophic plant. Given its special nutritional strategies and evolutionary significance, the mitogenome was first characterized, and three plastomes sampled from Asia were assembled. The plastomes were found to be the smallest among Orchidaceae, with lengths ranging from 18,339 to 19,047 bp, and exhibited high sequence variety. For the mitogenome, a total of 414,552 bp in length, comprising 26 circular chromosomes, were identified. A total of 54 genes, including 38 protein-coding genes, 13 tRNA genes, and 3 rRNA genes, were annotated. Multiple repeat sequences spanning a length of 203,423 bp (45.47%) were discovered. Intriguingly, six plastid regions via intracellular gene transfer and four plastid regions via horizontal gene transfer to the mitogenome were observed. The phylogenomics, incorporating 90 plastomes and 56 mitogenomes, consistently revealed the sister relationship of Epipogium and Gastrodia , with a bootstrap percentage of 100%. These findings shed light on the organelle evolution of Orchidaceae and non-photosynthetic plants.

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Background Hemerocallis citrina Baroni is a traditional vegetable crop widely cultivated in eastern Asia for its high edible, medicinal, and ornamental value. The phenomenon of codon usage bias (CUB) is prevalent in various genomes and provides excellent clues for gaining insight into organism evolution and phylogeny. Comprehensive analysis of the CUB of mitochondrial (mt) genes can provide rich genetic information for improving the expression efficiency of exogenous genes and optimizing molecular-assisted breeding programmes in H. citrina. Results Here, the CUB patterns in the mt genome of H. citrina were systematically analyzed, and the possible factors shaping CUB were further evaluated. Composition analysis of codons revealed that the overall GC (GCall) and GC at the third codon position (GC3) contents of mt genes were lower than 50%, presenting a preference for A/T-rich nucleotides and A/T-ending codons in H. citrina. The high values of the effective number of codons (ENC) are indicative of fairly weak CUB. Significant correlations of ENC with the GC3 and codon counts were observed, suggesting that not only compositional constraints but also gene length contributed greatly to CUB. Combined ENC-plot, neutrality plot, and Parity rule 2 (PR2)-plot analyses augmented the inference that the CUB patterns of the H. citrina mitogenome can be attributed to multiple factors. Natural selection, mutation pressure, and other factors might play a major role in shaping the CUB of mt genes, although natural selection is the decisive factor. Moreover, we identified a total of 29 high-frequency codons and 22 optimal codons, which exhibited a consistent preference for ending in A/T. Subsequent relative synonymous codon usage (RSCU)-based cluster and mt protein coding gene (PCG)-based phylogenetic analyses suggested that H. citrina is close to Asparagus officinalis, Chlorophytum comosum, Allium cepa, and Allium fistulosum in evolutionary terms, reflecting a certain correlation between CUB and evolutionary relationships. Conclusions There is weak CUB in the H. citrina mitogenome that is subject to the combined effects of multiple factors, especially natural selection. H. citrina was found to be closely related to Asparagus officinalis, Chlorophytum comosum, Allium cepa, and Allium fistulosum in terms of their evolutionary relationships as well as the CUB patterns of their mitogenomes. Our findings provide a fundamental reference for further studies on genetic modification and phylogenetic evolution in H. citrina.

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The plants of Orchidaceae are widely distributed in the world, 47 species of which have been used as folk medicines with a long history. The tubers and stems of them exhibit diverse efficacy, including clearing heat and resolving toxin, moistening lung and relieving cough and promoting blood circulation. Since dihydrophenanthrenes were responsible for the medical purposes, the characteristic skeletons, pharmacological effects and clinical applications of dihydrophenanthrenes were summarized in this review, so as to provide a theoretical basis for the comprehensive study, development and application of DPs from medicinal plants of Orchidaceae.

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Myanmar is situated in Southeast Asia, where species richness and diversity are very high. Myanmar orchid flora is very rich, but still poorly known because botanical explorations have sharply decreased in Myanmar since 1950. The present study provides a checklist of Myanmar orchid flora which includes 1040 species and 151 genera currently known from Myanmar, based on the herbarium specimens, literature and online databases. The number of species is increased by approximately 200 species more than that given in the checklist of Kress et al. (2003), mainly due to recent discoveries of new species to science and new records for Myanmar. There are 76 endemic species of Orchidaceae in Myanmar. It is estimated that ca. 150-300 species still remain as unidentified and are expected to be discovered in further studies on Myanmar orchid flora.

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